The Best Base for a Wood-fired Hot Tub and what You Need to Know about the Power Supply

Choose the right location first

Survey your property first to choose the best spot for your wood-fired spa. The ground must be level and strong enough to support a unit that can weigh 1,500+ kg when filled with water.

As a rule, smaller 1–2 person units and simpler off-grid models sit closer to 1.5 tonnes, while larger models with spa systems and filtration can reach around double that. Most brands list total filled weight on their product pages.

Wood burners produce smoke and occasional flying ash, so keep a safe clearance of at least 3 metres from surrounding objects. A chimney extension is often a smart addition to disperse smoke higher above the area.

Be considerate of your neighbours, too. If possible, place the hot tub away from nearby windows—even when no one complains about garden gatherings, smoke can make it uncomfortable to ventilate rooms or dry laundry outdoors while the water is heating.

Can a wood-fired hot tub be installed under a roof?

Many manufacturers allow installation under a roof only if it’s done by authorised safety specialists or approved installers. Roofed structures such as pergolas, gazebos, and covered terraces come with strict clearance and ventilation requirements. In most cases, wood-fired hot tubs are intended for outdoor use only. Sinking the tub into decking is also permitted by only a limited number of manufacturers.

How far should a wood-fired hot tub be located from the house?

Install your wood-fired hot tub as far from flammable objects and buildings as possible, but no less than 1–1.5 metres away. Also ensure the chimney top is at least 3 metres from nearby objects. Many specialists recommend chimney extensions to increase height.

Also consider drainage: plan where the water will go and remember that fire safety isn’t the only factor when choosing the right location.

How much space is needed around a hot tub?

Leave enough room to walk around the hot tub for maintenance and servicing. A practical guideline is at least 0.5–1 metre on all sides for access. You’ll typically need more space on the side with the steps and around the wood-burning stove for safe, comfortable use.

Prepare the base

The more solid the surface on which your hot tub is going to sit, the better. A concrete pad or stone pavement is ideal, and wooden or PVC deckings are similarly fabulous for the purpose and will provide an attractive look. Make sure to check with hot tub manufacturers to see whether they offer hot tub designs that can be sunk into the decking, and you should refuse if your chosen model cannot be recessed in the deck.

A major no-no when it comes to hot tub placement is to put it directly onto your lawn. This is because the vegetation underneath the unit will prevent proper ventilation. Most wood-fired hot tubs have a foundation structure made of wood, which tends to get affected by mould, and it can rot fairly quickly. Ensure you avoid this if you are planning on using your spa for more than one or two years. When you’re making such a big investment, no doubt you’ll want to enjoy it for many years to come!

The quickest and cheapest way to avoid this issue with base placement is to prepare your chosen foundation with gravel and then raise your hot tub on concrete slabs or bricks so as to leave the proper gap underneath the hot tub to facilitate the free flow of air for good ventilation.

What is the best base for a wood-fired hot tub?

Concrete, gravel and wooden deck are the top base choices to rest your wood-fired spa on. Each option comes with its own advantages and disadvantages which can be briefly summarised as follows.

Type of base	Pros	Cons
Concrete Photo credit: Gardenvity	• Extremely sturdy and long-lasting • Inexpensive	• May crack and form puddles or a slope if not installed correctly • Takes a longer time to install
Concrete slabs or pavement Photo credit: Royal Tubs	• Most sturdy and durable	• Expensive
Gravel (shingle or pea gravel) Photo credit: The Log Company (Kirami)	• Offers the best drainage • Least expensive • Easiest to install • Will not crack over time	• Cannot guarantee structural integrity over time if placed on relatively soft soil
Wooden/composite deck Photo credit: Skargards	• Most attractive • Solid and fairly durable	• Most expensive • Requires specialists to install • Requires maintenance to ensure durability

How heavy is a wood-fired hot tub?

A popular six-person model typically weighs approximately 280 kilograms, and around 2,000 kilograms when filled with water (exceeding the 2-tonne margin fairly easily when occupied by the maximum number of people). The total weight of the hot tub unit depends mainly on the size of the hot tub and the technology features used. For example, if the hot tub features steps, a cover and a water filtration system enclosed in a separate wooden cabinet, this may add some 70-100 kilograms to the weight of the hot tub itself. 

Is my deck strong enough for a hot tub?

Construction specialists have commented that, in general, a deck should be able to support approximately 100 pounds per square foot (45 kg per 0.1 m²) if it’s not raised higher than a couple of feet, so it should be perfectly safe to place your wood-fired spa on a deck.

Does a wood-fired hot tub have to be placed perfectly level?

Yes, it does. Any difference in the height of support at the hot tub contact points can cause unwanted structural changes over time. Make sure that each contact point is equally supported so no point is higher or lower than any other point. If the difference in height is visible to the naked eye, the water level at the opposite ends of the hot tub will be unequal too.

Can a hot tub be placed directly on grass?

This would be the worst thing to do. You should not place a wood-fired hot tub on a lawn or soil as it does not provide a solid base. Even slight differences in the height of support at the hot tub contact points can cause unwanted structural changes over time. In addition, when exposed to wet soil and grass, the wooden components can become damaged due to dampness and restricted ventilation, which will eventually promote quicker decay and rotting. Exposure to insects and other pests is also significantly higher when the hot tub is placed on grass, so it should be avoided.

Check your mains connections for your hot tub’s power supply

Wood-fired hot tubs tend to be upgraded with systems that add comfort and ease of use, as well as combined wattage on the electric lines. Therefore, you must make sure to carefully check the requirements with your hot tub manufacturer.

Usually, a wood-fired hot tub with a spa system and water filter will not require any special electric facilities, and you're good to go with a domestic mains outlet with 13 Amp cabling.

However, with more technology packed into the modern units, you may find yourself using a 2.2 kW hydrotherapy pump, a 700 W air jet compressor and a 3 kW electrical heater working simultaneously (that’s 5.9 kW of combined power). These cannot be plugged into a simple extension cable, and instead will require a stronger supply, which is typically 32 Amp. In such cases, it is essential to consult an authorised electrician to discuss your requirements and the electrical supply in your household. Even so, the power demand for your hot tub will not be as much as what an electric hot tub uses.

Ideally, you should contact the seller and ask about what is required. The next step would be to hire a qualified electrician to install the necessary electrical circuits and switchboard to ensure you comply with all safety requirements.

Preparing the base is all your responsibility

Make no mistake in thinking that a full hot tub installation service includes base preparation too. The reality is that preparing the space in your garden is all your responsibility to arrange. This requires a range of skills and tools to properly set up the spot for your hot tub compared to those involved in installing the tub itself. While some brands do offer a full hot tub installation service (such as Gardenvity and The Log Company), none will prepare the ground for you, so it is important that you do it first.

If you require assistance to prepare that space for your tub and need to hire someone for this, you can check out local contractors and find one who fits your needs.

Non-negotiable steps that can’t be skipped

Before getting a wood-fired hot tub, you must first check whether you live in a Smoke Control Area. If you’re unsure, you can check out this map on the Defra website for assistance. However, Defra also advises you to check with your local council for up to date information, since the data on the map is indicative only. If you live in the UK, you can find your local council here.